Figure 1: Myelogram of low back
showing bone spur lesion indenting
the nerve sac (white)

Myelograms are special X-ray studies of the spinal canal and spinal cord. They are used to diagnose and evaluate conditions affecting the spinal canal and nerve elements such as spinal stenosis, spinal cord impingement, and nerve root impingement. [figure 1] Myelograms are performed by injection a contrast agent into the spinal fluid via a lumbar puncture. A lumbar puncture is also called a spinal tap. After injection of the dye, multiple radiographs are taken, and the patient on the x-ray table is tilted head down to move the dye up the spinal canal as needed. After the x-rays, the second part of the study is a CT scan evaluation of the spinal region(s) of interest. Following the myelogram/CT scan, the patient is observed by the radiology staff for a few hours and then sent home. Myelograms can be useful after an MRI or if one cannot have an MRI. Myelograms are also commonly done for patients who have had previous spinal surgery including the use of metallic internal fixation rods, hooks, or screws.